U.S. patent application number 14/645163 was filed with the patent office on 2015-09-17 for method and apparatus for controlling interference in device-to-device communication.
The applicant listed for this patent is Research and Business Foundation Sungkyunkwan University, Samsung Electronics Co., Ltd.. Invention is credited to Min Jang, Jin Whan Kang, Dae-Gyun Kim, Sang-Hyo Kim, Myung Hoon Koh, Seung-Hoon Park, Hyun-Seok Ryu.
Application Number | 20150264695 14/645163 |
Document ID | / |
Family ID | 54070554 |
Filed Date | 2015-09-17 |
United States Patent
Application |
20150264695 |
Kind Code |
A1 |
Kim; Sang-Hyo ; et
al. |
September 17, 2015 |
METHOD AND APPARATUS FOR CONTROLLING INTERFERENCE IN
DEVICE-TO-DEVICE COMMUNICATION
Abstract
Disclosed is a method for controlling interference for D2D
communication. The method includes: identifying whether a position
of a first user device belongs to a first area that satisfies a
predetermined criterion; and if the position of the first user
device is identified to belong to the first area, determining some
resources constituting dedicated resources of the first area, among
available resources of a signal for discovering a counterpart user
device of D2D communication by the first user device, as resources
of the signal.
Inventors: |
Kim; Sang-Hyo; (Seoul,
KR) ; Ryu; Hyun-Seok; (Gyeonggi-do, KR) ; Kim;
Dae-Gyun; (Gyeonggi-do, KR) ; Park; Seung-Hoon;
(Seoul, KR) ; Kang; Jin Whan; (Gyeonggi-do,
KR) ; Koh; Myung Hoon; (Gyeonggi-do, KR) ;
Jang; Min; (Seoul, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Samsung Electronics Co., Ltd.
Research and Business Foundation Sungkyunkwan University |
Gyeonggi-do
Gyeonggi-do |
|
KR
KR |
|
|
Family ID: |
54070554 |
Appl. No.: |
14/645163 |
Filed: |
March 11, 2015 |
Current U.S.
Class: |
455/452.1 |
Current CPC
Class: |
H04W 8/005 20130101;
H04W 72/082 20130101 |
International
Class: |
H04W 72/08 20060101
H04W072/08 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 11, 2014 |
KR |
10-2014-0028290 |
Claims
1. A method for controlling interference for device to device (D2D)
communication, the method comprising: identifying whether a
position of a first user device belongs to a first area that
satisfies a predetermined criterion; and if the position of the
first user device is identified as belonging to the first area,
determining resources constituting dedicated resources of the first
area, among available resources of a signal for discovering a
counterpart user device of D2D communication by the first user
device, as resources of the signal.
2. The method of claim 1, wherein the predetermined criterion is a
number of power levels that are equal to or more than a
predetermined threshold of power level is equal to or more than a
predetermined value, among power levels that are obtained from
signals received from nearby user devices by the first user
device.
3. The method of claim 2, wherein the predetermined threshold of
power level is a default value configured by manufacturers or
communication service providers.
4. The method of claim 2, wherein the predetermined threshold of
power level is a value based on an accumulation of previously
received discovery signals and previous results of a dense area
determination.
5. The method of claim 2, wherein a predetermined threshold of
power level is based on a power noise (PN) level.
6. The method of claim 1, wherein determining the resources of the
signal comprises obtaining dedicated resource information on the
first area, and the dedicated resource information includes at
least one of a position of a subframe and a position of a
subcarrier, by which the dedicated resources start in the available
resources, and a ratio of the dedicated resources to the available
resources.
7. The method of claim 6, wherein determining the resources of the
signal comprises randomly selecting partial resources from among
the partial resources constituting the dedicated resources.
8. The method of claim 6, wherein determining the resources of the
signal comprises selecting partial resources constituting the
dedicated resources so that the partial resources are uniformly
allotted by a time unit.
9. The method of claim 6, wherein determining the resources of the
signal comprises selecting partial resources from among the partial
resources constituting the dedicated resources so that the selected
partial resources have constant intervals by a time unit and by a
frequency unit from partial resources that have been allotted to
other user devices.
10. The method of claim 1, wherein determining the resources of the
signal comprises allotting partial resources constituting the
remaining resources except for the dedicated resources among the
available resources to resources of a signal for discovering a
counterpart user device for D2D communication by an external user
device located outside the first area.
11. A user device for controlling interference for device to device
(D2D) communication, the user device comprising: a controller
configured to: identify whether a position of the user device
belongs to a first area that satisfies a predetermined criterion;
and if the position of the user device is identified as belonging
to the first area, determine resources constituting dedicated
resources of the first area, among available resources of a signal
for discovering a counterpart user device of D2D communication, as
resources of the signal.
12. The user device of claim 11, wherein the criterion is a number
of power levels that are equal to or more than a predetermined
threshold of power level is equal to or more than a predetermined
value, among power levels that are obtained from signals received
from nearby user devices by the first user device.
13. The method of claim 12, wherein the predetermined threshold of
power level is a default value configured by manufacturers or
communication service providers.
14. The method of claim 12, wherein the predetermined threshold of
power level is a value based on an accumulation of previously
received discovery signals and previous results of a dense area
determination.
15. The method of claim 12, wherein a predetermined threshold of
power level is based on a power noise (PN) level.
16. The user device of claim 10, wherein the controller is further
configured to determine the resources of the signal as some of the
resources corresponding to the dedicated resource information on
the first area, which is obtained through a transmitting/receiving
unit, and the dedicated resource information includes at least one
of a position of a subframe and a position of a subcarrier, by
which the dedicated resources start in the available resources, and
a ratio of the dedicated resources to the available resources.
17. The user device of claim 16, wherein the controller is further
configured to randomly select partial resources from among the
partial resources constituting the dedicated resources.
18. The user device of claim 16, wherein the controller is further
configured to select partial resources constituting the dedicated
resources so that the partial resources are uniformly allotted by a
time unit.
19. The user device of claim 16, wherein the controller is further
configured to select partial resources from among the partial
resources constituting the dedicated resources so that the selected
partial resources have constant intervals by a time unit and by a
frequency unit from partial resources that have been allotted to
other user devices.
20. The user device of claim 19, wherein the controller is further
configured to allot partial resources constituting the remaining
resources except for the dedicated resources among the available
resources to resources of a signal for discovering a counterpart
user device for D2D communication by an external user device
located outside the first area.
Description
CROSS-REFERENCE TO RELATED APPLICATION AND CLAIM OF PRIORITY
[0001] The present application is related to and claims the
priority under 35 U.S.C. .sctn.119(a) to Korean Application Serial
No. 10-2014-0028290, which was filed in the Korean Intellectual
Property Office on Mar. 11, 2014, the entire content of which is
hereby incorporated by reference.
TECHNICAL FIELD
[0002] The present disclosure relates to a method and an apparatus
for controlling interference in device-to-device communication.
BACKGROUND
[0003] In typical mobile communication systems, user devices in a
limited area share limited resources, such as, time, frequency, or
the like, for use. If a large number of user devices exist in a
specific area, the communication resources allotted to each user
device can be decreased. In such an environment, most user devices
may not have satisfactory communication services provided. The
typical mobile communication systems have adopted methods of using
base stations, such as small cells, or heterogeneous networks, in
order to cope with the problem of a high density of user devices.
More specifically, small base stations or repeaters are installed
in an area (hereinafter, referred to as a "dense area"), such as
shopping malls, airports, or the like, where many people gather, to
deal with heavy traffic, and Wi-Fi access points (AP) are installed
to distribute traffic through the heterogeneous network. In a
specific area where people gather in specific season, for example,
in a downtown area in Christmas season, mobile base stations are
disposed to be prepared for a heavy increase in traffic.
[0004] Compared to the mobile communication systems above, in
device-to-device (D2D) communication that is one of the distributed
communication systems in which communication is made without
utilizing infrastructure, such as base stations, or Wi-Fi APs, the
user device should perform most operations for communication by
itself. Therefore, the methods described above to deal with heavy
traffic in a dense area in the typical mobile communication systems
are hardly applied to the D2D communication. Thus, a specific
method for controlling interference of the dense area in the
distributed communication environment is required.
SUMMARY
[0005] To address the above-discussed deficiencies, it is a primary
object to provide a method and an apparatus for managing resources
in a dense area and controlling interference in a distributed
communication environment such as D2D communication.
[0006] The present disclosure provides a method and an apparatus by
which each user device for D2D communication determines the dense
area by itself, and if the entry of the user device into the dense
area is identified, interference is controlled using resource
partition.
[0007] In accordance with an aspect of the present disclosure, a
method for controlling interference for D2D communication includes:
identifying whether the position of the first user device belongs
to the first area that satisfies a predetermined criterion; and if
the position of the first user device is identified as belonging to
the first area, determining some of the resources constituting
dedicated resources of the first area, among available resources of
a signal for discovering a counterpart user device of D2D
communication by the first user device, as resources of the
signal.
[0008] In accordance with another aspect of the present disclosure,
a user device for controlling interference for D2D communication
includes: a controller that identifies whether the position of the
user device belongs to the first area that satisfies a
predetermined criterion, and if the position of the user device is
identified as belonging to the first area, determines some of the
resources constituting dedicated resources of the first area, among
available resources of a signal for discovering a counterpart user
device of D2D communication, as resources of the signal.
[0009] According to embodiments of the present disclosure, the user
device for D2D communication determines whether its own position
belongs to the dense area by itself, and if the user device is
located in the dense area, resources for transmitting a discovery
signal are selected from among dedicated resources of the dense
area in available resources, so interference created by other
devices is reduced.
[0010] Before undertaking the DETAILED DESCRIPTION below, it may be
advantageous to set forth definitions of certain words and phrases
used throughout this patent document: the terms "include" and
"comprise," as well as derivatives thereof, mean inclusion without
limitation; the term "or," is inclusive, meaning and/or; the
phrases "associated with" and "associated therewith," as well as
derivatives thereof, may mean to include, be included within,
interconnect with, contain, be contained within, connect to or
with, couple to or with, be communicable with, cooperate with,
interleave, juxtapose, be proximate to, be bound to or with, have,
have a property of, or the like; and the term "controller" means
any device, system or part thereof that controls at least one
operation, such a device may be implemented in hardware, firmware
or software, or some combination of at least two of the same. It
should be noted that the functionality associated with any
particular controller may be centralized or distributed, whether
locally or remotely. Definitions for certain words and phrases are
provided throughout this patent document, those of ordinary skill
in the art should understand that in many, if not most instances,
such definitions apply to prior, as well as future uses of such
defined words and phrases.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] For a more complete understanding of the present disclosure
and its advantages, reference is now made to the following
description taken in conjunction with the accompanying drawings, in
which like reference numerals represent like parts:
[0012] FIG. 1A illustrates an example of a mesh network to describe
a general device discovery process according to various embodiments
of the present disclosure;
[0013] FIG. 1B illustrates a typical timing structure for device to
device (D2D) communication according to various embodiments of the
present disclosure;
[0014] FIG. 2 illustrates a typical resource allotment structure
for D2D communication according to various embodiments of the
present disclosure;
[0015] FIG. 3 illustrates an example in which a user device
determines whether the user device exists within a dense area
according to a dense area determination criterion according to
various embodiments of the present disclosure;
[0016] FIG. 4 illustrates interference with a user device located
in a dense area by other user devices in the same dense area
according to various embodiments of the present disclosure;
[0017] FIG. 5a illustrates a resource partitioning method by a
sub-frame unit according to various embodiments of the present
disclosure;
[0018] FIG. 5b illustrates a resource partitioning method by a
subcarrier unit according to various embodiments of the present
disclosure;
[0019] FIGS. 6A and 6B illustrate an example of a random resource
area selection method by which dense area discovery resources are
selected to be different in each dense area according to various
embodiments of the present disclosure;
[0020] FIG. 7 illustrates overall operations of a resource
partitioning method according to various embodiments of the present
disclosure;
[0021] FIG. 8 illustrates an operation of obtaining information on
dense area discovery resources through a peripheral device
installed in a permanent dense area according to various
embodiments of the present disclosure;
[0022] FIG. 9 illustrates an operation of obtaining information on
dense area discovery resources in a dense area other than a
permanent dense area according to various embodiments of the
present disclosure;
[0023] FIG. 10A illustrates a method for randomly selecting a
discovery resource block (DRB) of a user device from among dense
area discovery resources according to various embodiments of the
present disclosure;
[0024] FIG. 10B illustrates an example of a method for selecting a
DRB of a user device from among dense area discovery resources
according to various embodiments of the present disclosure;
[0025] FIG. 10C illustrates an example of a method for selecting a
DRB of a user device from among dense area discovery resources
according to certain embodiments of the present disclosure;
[0026] FIG. 11 illustrates an example of a resource partitioning
method for an external area according to various embodiments of the
present disclosure;
[0027] FIG. 12 illustrates examples of a DRB selection method
according to various embodiments of the present disclosure;
[0028] FIG. 13 illustrates the operation of a user device according
to various embodiments of the present disclosure;
[0029] FIG. 14 illustrates a user device according to various
embodiments of the present disclosure;
[0030] FIG. 15 illustrates an example of a network environment to
which a resource partition is applied according to various
embodiments of the present disclosure;
[0031] FIG. 16 illustrates the performance result if a resource
partition is applied to a single discovery section according to
various embodiments of the present disclosure;
[0032] FIG. 17 illustrates the performance result of each area
where a resource partition is applied according to various
embodiments of the present disclosure; and
[0033] FIG. 18 illustrates the performance result if a resource
partition is applied to a repetition discovery section according to
various embodiments of the present disclosure.
DETAILED DESCRIPTION
[0034] FIGS. 1A through 18, discussed below, and the various
embodiments used to describe the principles of the present
disclosure in this patent document are by way of illustration only
and should not be construed in any way to limit the scope of the
disclosure. Those skilled in the art will understand that the
principles of the present disclosure may be implemented in any
suitably arranged wireless communications system. Hereinafter, the
operation of a preferred embodiment of the present disclosure will
be described in detail with reference to the accompanying drawings.
Like reference numerals designate like components in the drawings
where possible even though components are shown in different
drawings. In the following description of the present disclosure, a
detailed description of related known functions or configurations
will be omitted so as not to obscure the subject of the present
disclosure. The terms as described below are defined in
consideration of the functions in the embodiments, and the meaning
of the terms varies according to the intention of a user or
operator, convention, or the like. Therefore, the definitions of
the terms should be determined based on the contents throughout the
specification.
[0035] In order to perform typical device to device (D2D)
communication, a device discovery process, by which each user
device discovers a distance enabling D2D communication and other
user devices for D2D communication, is performed. The device
discovery process is a prerequisite to an actual communication
process of configuring a link between the user devices for D2D
communication and transmitting or receiving data through the
link.
[0036] FIG. 1A illustrates an example of a mesh network to describe
a general device discovery process according to various embodiments
of the present disclosure.
[0037] Referring to FIG. 1A, seven user devices, such as the first
user device 100 to the seventh user device 112, perform the device
discovery process.
[0038] In addition, FIG. 1B illustrates a typical timing structure
for D2D communication according to various embodiments of the
present disclosure.
[0039] Referring to FIG. 1B, time sections for D2D communication
includes a synchronizing section 114 in which one user device is
synchronized with the other user device, a discovery section 116 in
which one user device performs a process of discovering the other
user device for D2D communication, a paging section 118 for
transmitting a paging signal, and a D2D communication section 120
for transmitting and receiving data for D2D communication between
one user device and the other user device. The sections except for
the discovery section 116 are the same as those of typical D2D
communication, so the detailed description thereof will be omitted
here.
[0040] More specifically, in the discovery section 116, the first
user device 100 to the seventh user device 112 broadcast
information including a network address, which is necessary for
device discovery, to be received by nearby user devices and decodes
signals broadcast by other user devices to identify discovery
information of the nearby user devices.
[0041] FIG. 2 illustrates a typical resource allotment structure
for D2D communication according to various embodiments of the
present disclosure.
[0042] Referring to FIG. 2, for example, the first user device 202
performs D2D communication. In certain embodiments, the first user
device 202 performs a device discovery process for identifying the
distance 200, in which D2D communication is available, and
information on the nearby user devices, for example, the second
user device 206, the third user device 206, and the fourth user
device 208, which are located within the available distance for D2D
communication. The timing structure 202 for D2D communication is
the same as that of FIG. 1B, so the detailed description thereof
will be omitted. Communication resources (hereinafter, referred to
as "entire discovery resources"), which are comprised of separate
times and frequencies, are allotted to the discovery section 116 of
the timing structure 220. Since the entire discovery resources
allotted to the discovery section 116 are shared by all of the user
devices that are located in a predetermined coverage, the device
discovery process is based on a multiple-access communication
method. The discovery signal transmitted by a main user device for
discovering a counterpart user device for D2D communication is
shorter than a normal message used in typical communications. The
user devices located in the coverage broadcast the discovery signal
using some of the entire discovery resources allotted to the
discovery section 116. Referring to FIG. 2, with regard to some of
the entire discovery resources, for example, the discovery signal
is broadcast using one of discovery resource blocks (DRB) that are
comprised of partial time and partial frequency, which have the
same time interval, among times and frequencies corresponding to
the entire discovery resources allotted to the discovery section
116. In FIG. 2, dotted or hatched blocks denote DRBs allotted to
the user device. Since D2D communication does not consider
infrastructure, such as base stations for allotting exclusive
resources to the user devices, each user device should select the
DRB for transmitting the discovery signal by itself.
[0043] The device discovery process is performed in the dense area.
In certain embodiments, the main user device should share the DRBs
of the entire discovery resources allotted to the discovery section
116 with other user devices, so the main user device is likely to
select the same DRB as that of other user devices. Moreover, the
user device located in the dense area is more influenced by
interference, compared to the user device (hereinafter, referred to
as an "external user device") that is located outside the dense
area.
[0044] Hereinafter, the embodiment of the present disclosure
provides a discovery environment self-determination method by which
the user device for D2D communication determines whether its own
position belongs to the dense area by itself, in order to improve
performance of the device discovery process for D2D communication.
The various embodiments of the present disclosure provide a method
by which, if the user device determines that its own position
belongs to the dense area, the user device allots dedicated
resources to the dense area using resource partition, power
control, or discovery period control, in order to reduce
interference created in the device discovery process. The various
embodiments of the present disclosure are applied to the
distributed communications set forth above, and D2D communication
that is one of the distributed communications will be described in
relation to the various embodiments of the present disclosure.
[0045] Discovery Environment Self-Determination Method
[0046] According to various embodiments of the present disclosure,
the user device for D2D communication identifies whether its own
position belongs to the dense area using a statistical analysis
method of reception power. According to the various embodiments of
the present disclosure, in a statistical analysis method of
reception power, power of the discovery signal received by the user
device is turned into data to be thereby analyzed in a statistical
method, regardless of the content of information included in the
received discovery signal. The discovery signal, according to
various embodiments of the present disclosure, does not include any
information on the device discovery environment. Thus, overhead is
not generated as well.
[0047] Hereinafter, the dense area is defined as follows in the
various embodiments of the present disclosure. More specifically,
in terms of mathematics, the dense area is defined as an
environment in which at least a predetermined number of user
devices exist in a specific area (such as at least "Y" nearby user
devices exist within a distance of "X" meters from the user
device). In certain embodiments, if the user devices are uniformly
distributed within the distance of "X" meters, "X" and "Y" are
configured as the numbers favorable to measurement and calculation.
For example, "X" and "Y" are configured as "tens of meters" and
"tens of devices," respectively. The mathematical definition about
the dense area is used for a criterion by which the user device
determines whether its own position belongs to the dense area. The
user device, according to various embodiments of the present
disclosure, determines a distance to the other user device located
in the dense area by measuring power of the reception signal. The
shorter the physical distance is between the user devices, the
better the visibility that is obtained. A pair of user devices that
have a short physical distance between them is more likely to
secure a line of sight. Accordingly, if the user device exists in
the dense area, a distance between user devices in the dense area
is relatively short. Thus, the user device in the dense area is
likely to receive a plurality of discovery signals having
relatively high power. According to the various embodiments of the
present disclosure, the user device identifies a power level of the
DRB allotted to the discovery signal that is received from the
nearby user device. If the result of the identification satisfies a
criterion that the number of DRBs having power equal to or more
than a specific level exceeds a predetermined value (hereinafter,
referred to as a "criterion for dense area determination"), the
user device determines that its own position belongs to the dense
area.
[0048] More specifically, the user devices, according to certain
embodiments of the present disclosure, defines "a specific power
level" and "a predetermined number" of DRBs having power equal to
or more than the specific power level, which are factors of the
criterion for dense area determination, as follows.
[0049] According to the various embodiments of the present
disclosure, a power noise (PN) level is measured in order to
determine the "specific power level" that is a criterion of a power
level of the discovery signal received by the user device. For
example, a thermal noise power level is easily obtained in most
communication systems, and usually, is measured in the external
frequency band other than the normal frequency band. If the thermal
noise power level is not available, the lowest value among power
levels of the DRBs measured in the received discovery signals is
regarded as the thermal noise power. In certain embodiments, an
average value of the DRBs of a specific percentage, which have the
lowest power value, is used for the thermal noise power value. The
thermal noise power value, such as the power level, is given in a
decibel (dB) unit.
[0050] The number of DRBs having power equal to or more than
"PN+.alpha." dB, such as the criterion for dense area determination
that is determined based on the configured thermal power noise
(PN), is measured from among the DRBs of the received discovery
signals. If the measured number of DRBs exceeds a predetermined
value .lamda., the user device determines that its own position
belongs to the dense area. The criterion for dense area
determination is based on the mathematical definition of the dense
area. Based on the mathematical definition of the dense area where
"Y" user devices exist within a radius of "X," the thermal-signal
to noise ratio (SNR) .alpha. is determined to reflect the radius of
"X", considering a path loss model. The predetermined value .lamda.
is configured in consideration of "Y." The user device identifies
that at least .lamda. nearby user devices have transmitted signals
more than SNR .alpha. through the operation above.
[0051] FIG. 3 illustrates an example of operation in which a user
device determines whether its own position belongs to the dense
area according to the criterion for dense area determination
according to various embodiments of the present disclosure.
[0052] Referring to FIG. 3, it is determined that the user device
is located in the dense area in the case of a dotted line 302 in
which the number of DRBs having signals equal to or more than SNR
.alpha. (see 300) exceeds the predetermined value X, provided that
SNR .alpha. is configured, for example, to be -70 dB. If the number
of DRBs having signals equal to or more than SNR .alpha. does not
exceed the predetermined value .lamda. (see 304), the user device
is determined to be located outside the dense area.
[0053] As described above, each user device determines whether its
own position belongs to the dense area, based on the criterion for
dense area determination defined by .alpha. and .lamda.. In certain
embodiments, the more accurate parameters, such as .alpha. and
.lamda., which constitute the criterion for dense area
determination, are, the more accurate the determination for the
dense area are. To this end, the parameters of .alpha. and .lamda.
are configured as default values by manufacturers or communication
service providers in a static method in which the user device uses
the parameters of the configured default values. In certain
embodiments, in a learning method, the user device accumulates
previously received discovery signals and previous results of dense
area determination and selects the parameters for use based on the
accumulation.
[0054] Method for Reducing Interference in Device Discovery
Process
[0055] Meanwhile, the performance of the user device located in the
dense area is degraded due to interference of discovery signals of
other user devices in the same dense area. Therefore, the
embodiment of the present disclosure provides a resource
partitioning method for regulating interference by signals of other
user devices in the dense area if the user device in the same dense
area performs the device discovery process.
[0056] FIG. 4 illustrates interference with a user device located
in a dense area by other user devices in the same dense area
according to various embodiments of the present disclosure.
[0057] Referring to FIG. 4, for example, the first user device 402
moves to the dense area. The first user device 402 has identified
that its own position belongs to the dense area 400 according to
the criterion for dense area determination set forth above. As
shown in FIG. 4, distances between the user devices in the same
dense area are quite short, such as less than tens of meters, and
discovery signals of the user devices exhibit relatively low path
loss. Therefore, the first user device 402 receives discovery
signals of enough power to be decoded from other user devices in
the same dense area. In addition to the discovery signals of other
user devices, the first user device 402 receives in-band emission
(IBE) interference of high power due to the discovery signals. In
certain embodiments, the IBE is a natural phenomenon by which power
of discovery signals transmitted through a specific subframe (time)
and a specific band (frequency) interferes with other bands of the
same subframe in part, which results from signal transmission. For
example, if the second user device 404 and the third user device
406 select the DRB corresponding to a frequency band different from
that of the first user device 402 in the same subframe, the first
user device 402 detects the IBE interference due to the discovery
signals transmitted by the second user device 404 and the third
user device 406. If the user devices in the same dense area select
the DRBs for the discovery signals (such as sub-blocks dotted or
hatched in the entire discovery resources 410) from among all of
the subframes constituting the entire discovery resources 410, the
selected DRBs acts as high IBE interference. Thus, as shown in FIG.
4, the discovery signal transmitted by the user device, such as the
second user device 404, which is located in a distance in which the
second user device be identified in the case of no interference, is
not likely to be decoded due to the IBE interference from other
user devices in the dense area 400.
[0058] Accordingly, the present disclosure provides a resource
partitioning method by which some of the entire available resources
(hereinafter, referred to as "entire discovery resources") allotted
for the discovery signals of the user devices are used as resources
(hereinafter, referred to as "dense area discovery resources") for
the discovery signals by the user devices located in the dense
area. The resource partitioning method is divided into a type of a
subframe unit and a type of a subcarrier unit according to
embodiments.
[0059] FIG. 5A illustrates a resource partitioning method by a
sub-frame unit according to certain embodiments of the present
disclosure. The embodiment of FIG. 5A provides a method by which
the user devices in the same dense area select the DRBs for
discovery signals from among some of the subframes constituting the
entire discovery resources, and transmit the discovery signals
using the selected DRBs. In FIG. 5A, the first user device 501 has
identified that its own position belongs to the dense area 500
based on the criterion for dense area determination set forth
above. In certain embodiments of the present disclosure, the first
user device 501 identifies whether its own position belongs to the
dense area 500 using the nearby user devices, if nearby user
devices are around the first user device 501 in the dense area 500.
Furthermore, the first user device 501 includes information stating
that the current dense area 500 is the dense area defined in the
present disclosure and discovery signals received from the nearby
user devices during the reception of the discovery signals. The
detailed description thereof will be described with reference to
FIG. 7. The first user device 501 obtains information on resources
available for discovery signals in the dense area 500, such as the
information on dense area discovery resources. The information on
dense area discovery resources is obtained from the nearby user
devices or by analyzing the discovery signals of other user devices
located in the dense area 500, according to various embodiments.
The obtaining operation will be described in detail later.
[0060] Referring to FIG. 5A, the discovery resources 504 for the
dense area 500 is defined as a partial area 504 corresponding to
some of the subframes constituting the entire discovery resources
502. Accordingly, if the first user device 501 identifies the
position of the dense area discovery resources 504, the first user
device 501 selects the DRB for transmitting its own discovery
signal from among the dense area discovery resources 504 and
transmits the discovery signal using the selected DRB.
[0061] FIG. 5B is a diagram to describe a resource partitioning
method by a subcarrier unit according to various embodiments of the
present disclosure.
[0062] In FIG. 5B, the second user device 511 has identified that
its own position belongs to the dense area 510 based on the
criterion for dense area determination set forth above. According
to certain embodiments of the present disclosure, the second user
device 511 identifies whether its own position belongs to the dense
area 510 using the nearby user devices.
[0063] The second user device 511 obtains information on resources
available for discovery signals in the dense area 510, such as
information on dense area discovery resources. The information on
dense area discovery resources is obtained from the nearby user
devices or by analyzing the discovery signals of other user devices
located in the dense area 510, according to certain embodiments.
The obtaining operation will be described in detail later.
[0064] Referring to FIG. 5B, the discovery resources 514 for the
dense area 510 is defined as a partial area 514 corresponding to
some of the subcarriers constituting the entire discovery resources
502. If the second user device 511 identifies the position of the
dense area discovery resources 514, the second user device 511
selects the DRB for transmitting its own discovery signal from
among the dense area discovery resources 514 and transmits the
discovery signal using the selected DRB.
[0065] According to various embodiments of the present disclosure,
it is considered to partition the entire discovery resources into
dense area discovery resources corresponding to some of the
subframes and some of the subcarriers.
[0066] According to various embodiments of the present disclosure,
there is no limit to the resource area where the user device
(hereinafter, referred to as an "external user device"), located
outside the dense area (hereinafter, referred to as a "non-dense
area"), selects the DRB for the discovery signal. The external user
device selects the DRB from among the entire discovery resources
and transmits the discovery signal using the same. According to
certain embodiments, the external user device selects the DRB for
the discovery signal from among the remaining resources except for
the dense area discovery resources in the entire discovery
resources. If the external user device selects the DRB for the
discovery signal from among the remaining resources except for the
dense area discovery resources, the discovery signal of the
external user device has a relatively high
signal-to-interference-to-noise ratio (SINR). Because the discovery
signal of the external user device is less vulnerable to
interference due to transmission of the discovery signals by the
user devices located in the dense area, the possibility of
discovery is increased.
[0067] In certain embodiments of the present disclosure, the
selectable subframe area or subcarrier area is selected to be
different by each dense area, in order to obtain the diversity
effect due to the resource partition described above.
[0068] FIGS. 6A and 6B illustrate an example of a random resource
area selection method by which dense area discovery resources are
selected to be different by each dense area according to various
embodiments of the present disclosure. In certain embodiments, a
ratio of dense area discovery resources that is selected from the
entire discovery resources in each dense area, such as a dense area
A 600 and a dense area B 610 is predetermined. The ratio of dense
area discovery resources is configured to be the same for each
dense area. In certain embodiments, the ratio of dense area
discovery resources is configured to be different in consideration
of characteristics of each dense area such as the number of user
devices in the dense area, a physical range of the dense area, or
the like. For convenience of explanation, the ratios of dense area
discovery resources in the dense area A 600 and the dense area B
610 are the same. In certain embodiments, the resource partition of
each dense area is randomly determined based on the ratio. Shown in
FIG. 6A, a start position 606 of subframes constituting the dense
area discovery resources for the dense area A 600 is randomly
determined in each dense area according to the various embodiments.
The resources corresponding to the subframes of a determined ratio
608 from the start position 606 are selected from the entire
discovery resources 604. The entire discovery resources are limited
to a predetermined time area and a predetermined frequency area. In
certain embodiments, the horizontal axis of the entire discovery
resources 604 corresponds to a time area and the vertical axis
corresponds to a frequency area. In FIG. 6B, a start position 614
of the subframes constituting the discovery resources for the dense
area "B" 610 is configured, for example, as the position spaced a
ratio of "a" from the end of the time area constituting the entire
discovery resources 604. In certain embodiments, partial subframes
corresponding to the ratio of "a" from the subframe start position
614 and partial subframes corresponding to the ratio of "b" from a
start position of the subframes corresponding to the entire
discovery resources 604 are selected as the resources corresponding
to the ratio of "a+b" of the discovery resources for the dense area
"B" 610. Likewise, each dense area independently selects available
resource areas. According to the various embodiments of the present
disclosure, the user device obtains information on the subframe
start position of the dense area and the ratio of the subframes to
the entire subframes, such as dense area discovery-related
information, and selects the corresponding resources. In FIGS. 6A
and 6B, the user device located in the dense area obtains the dense
area discovery resources by a subframe unit. According to certain
embodiments, the user device located in the dense area obtains the
dense area discovery resources by a subcarrier unit or by a
combination of a subframes unit and a subcarrier unit. The resource
portioning method according to various embodiments of the present
disclosure will be described in detail with reference to FIGS. 10A
to 10C.
[0069] FIG. 7 illustrates a diagram to describe overall operations
of a resource partitioning method according to certain embodiments
of the present disclosure.
[0070] In FIG. 7, the first user device 702 moves to a dense area
700. In operation 701, the first user device 702 identifies whether
its own position belongs to the dense area 700. According to
certain embodiments, the first user device 702 identifies whether
the criterion for dense area determination set forth above is
satisfied or obtains information on whether the first user device
702 is located in the dense area 700 from peripheral devices or
nearby user devices (see 708a). In certain embodiments, the
peripheral devices are base stations, repeaters, Wi-Fi APs, radio
frequency identification (RFID) units, infrared sensors, or the
like. The peripheral device 704 for providing information on the
dense area 700 is installed. In certain embodiments, the user
device entering the dense area 700, such as the first user device
702, receives the information on the dense area 700 (see 708b)
transmitted by the peripheral device 704, to determine whether the
first user device 702 has entered the dense area. In certain
embodiments, the first user device 702 identifies the dense area
entry information included in the discovery signal that is
periodically transmitted by the nearby user device, such as the
first nearby user device 706 that recognizes the dense area 700
(see 708a), to determine the entry of the first user device into
the dense area.
[0071] For example, if the first user device 702 recognizes that
its own position belongs to the dense area 700, the first user
device 702 obtains information on the discovery resources for the
dense area 700 through one of the operation 708a or 708b, such as
through the first nearby user device 706 or the peripheral device
704. In certain embodiments, the information on the dense area
discovery resources is expressed as a start position of subframes
of the discovery resources for the dense area 700 in the entire
discovery resources 712 and a ratio of the discovery resources for
dense area 700 to the entire discovery resources 712. The start
position of the subframes is expressed as a subcarrier position, or
a combination of a subframe position and a subcarrier position
according to another embodiment of the present disclosure.
[0072] The information on the discovery resources for the dense
area 700 is obtained by receiving the information from the nearby
user device (such as see 704 of FIG. 7) or by analyzing the
discovery signal of the nearby user device. If a multitude of user
devices in a building where many people gather in a dense area 700,
such as a shopping mall, an airport, an office, or the like such a
building is regarded as a permanent dense area. In order to
effectively deal with traffic between the user devices in the
permanent dense area in the typical mobile communication system,
peripheral devices, such as repeaters, Wi-Fi APs, or the like, are
separately installed in the building. Spatial characteristics of
the building facilitate installation of various communication
auxiliary devices, such as RFID units, infrared sensors, or the
like. The infrastructure for communication between the user devices
is well established in various ways.
[0073] FIG. 8 illustrates an operation of obtaining information on
the dense area discovery resources through a peripheral device
installed in the permanent dense area according to various
embodiments of the present disclosure.
[0074] In FIG. 8, an auxiliary device 808 is installed at the
entrance of the permanent dense area 810, and the user device 802
moves to the permanent dense area 810 (see 804). During the
movement, the user device 802 receives information on discovery
resources for the permanent dense area 810 that is transmitted by
the auxiliary device 808 at the entrance of the permanent dense
area 810 in operation 806. The auxiliary device 808 is configured
to detect the entry of the user device 802 into a predetermined
area, and to transmit the information on discovery resources for
the permanent dense area 810. According to various embodiments of
the present disclosure, the user device 802 recognizes its own
entry into the permanent dense area 810, and then makes a request
to the auxiliary device 808 for the information on discovery
resources for the permanent dense area 810.
[0075] FIG. 9 illustrates an operation of obtaining information on
dense area discovery resources in a dense area other than the
permanent dense area according to various embodiments of the
present disclosure.
[0076] In FIG. 9, a user device 902 moves to a dense area 900, and
other user devices located in the dense area 900 have selected DRBs
for the discovery signals from the dense area discovery resources
that are determined by the resource portioning method according to
the present disclosure.
[0077] If the discovery signals transmitted by the user devices
located in the dense area 900 include information on resources that
are selected from among the discovery resources for the dense area
900, the user device 902 obtains the selectable resource
information through the discovery signal of at least one of other
user devices located in the dense area 900 in operation 904. In
certain embodiments, the user device obtains the selectable
resource information included in the discovery signals of other
user devices, whereas overhead occurs due to transmission of the
discovery signals including the selectable resource information by
the user devices in the dense area.
[0078] In certain embodiments, other user devices located in the
dense area 900 transmit the discovery signals do not include the
selectable resource information. In certain embodiments, the
counterpart user device 902 estimates the selectable resources of
the entire discovery resources based on power of the discovery
signals received from other user devices.
[0079] The user device 902 obtains the selectable resource
information from the discovery signals of other user devices or
selects the DRB for its own discovery signal from among the
selectable resources, based on the estimated selectable resource
information. If the user device 902 should repeatedly transmit the
discovery signal, the DRB is selected at random or using a
predetermined pattern such as a Latin square from among the
selectable resources. According to certain embodiments of the
present disclosure, in the dense area resource partition, the DRB
is selected in three ways as shown in FIGS. 10A to 10C, according
to the operation of the user device and the installation of the
peripheral device.
[0080] FIG. 10A illustrates an example of a method for randomly
selecting the DRB of a user device from among dense area discovery
resources according to various embodiments of the present
disclosure. Hereinafter, for convenience of explanation, a user
device 1002 in FIGS. 10A to 10C has recognized that its own
position belongs to a dense area 1000 and the user device 1002
corresponds to the user device 902 of FIG. 9, which obtains the
selectable resource information with respect to the dense area
1000. The selected DRBs from among the DRBs constituting the dense
area discovery resources 1006 in the entire discovery resources
1004 are dotted and hatched.
[0081] Referring to FIG. 10A, the user device 1002 randomly selects
one DRB 1008 from among the selectable DRBs of the DRBs
constituting the discovery resources 1006 for the dense area 1000
where the user device 1002 is located based on selectable resource
area information.
[0082] FIG. 10B illustrates another example of a method for
selecting the DRB of the user device from among dense area
discovery resources according to various embodiments of the present
disclosure.
[0083] Since the IBE interference set forth above influences other
DRBs constituting the same subframe of a corresponding signal, the
DRBs is uniformly selected by each subframe in order to reduce the
IBE interference. In certain embodiments, the user device 1002 of
FIG. 10b identifies DRB information selected by the user device
from the discovery signals of other user devices located in the
dense area 1000. The user device 1002 measures power of each
subframe constituting the discovery resource 1006 for the dense
area 1000. The user device 1002 randomly selects one DRB 1018 from
the subframe having the lowest power. The uniform DRBs, such as the
three DRBs by each subframe constituting the dense area discovery
resources 1006, are selected.
[0084] FIG. 10C illustrates still another example of a method for
selecting DRBs of a user device in dense area discovery resources
according to various embodiments of the present disclosure. In
certain embodiments, a peripheral device 1004 is installed to
manage the dense area 1000 and minimize the IBE interference. The
IBE interference is severe in the DRB closer to the DRB
transmitting the discovery signal of the user device. In certain
embodiments, the peripheral device 1004 allots the DRBs of the user
devices located in the dense area 1000 to be distributed. According
to certain embodiments, the peripheral device 1004 has recognized
the DRB use status of each user device in the discovery resources
1006 for the dense area 1000. If a request for allotting the DRBs
is received from the user device 1002, the peripheral device 1004
selects the DRB 1028 spaced a constant distance from the subframes
and the subcarriers of the DRBs, which have been allotted to other
user devices, from among the available DRBs of the discovery
resources 1006 for the dense area 1000 in the entire discovery
resources 1004.
[0085] In certain embodiments of the present disclosure, the DRBs
for the discovery signals of the external user devices is allotted
to the remaining area except for the dense area discovery resources
in the entire discovery resources.
[0086] FIG. 11 illustrates an example of a resource partitioning
method for an external area according to various embodiments of the
present disclosure.
[0087] Referring to FIG. 11, the first user device 1102 located in
a dense area 1100 selects one of the DRBs constituting a discovery
resource area 1108 for the dense area in the entire discovery
resources 1106. A user device located outside the dense area 1100,
such as an external user device 1104, selects one of the DRBs
constituting the remaining area (hereinafter, referred to as an
"external resource area" 1109), except for the discovery resource
area 1108, for the dense area in the entire discovery resources
1106. In certain embodiments, the resources are exclusively
allotted to the user devices located in the dense area and the
external user devices, respectively, through the resource
allotment.
[0088] In certain embodiments, the external user device 1104
obtains information on the external resource area 1109. If the
external user device 1104 escapes from the dense area 1100, the
user device selects the DRB for the discovery signal from the
remaining area except for the dense area discovery resources 1108
that are preliminary obtained in the entire discovery resources
1106. In certain embodiments, a base station serving the escaped
external user device 1104 allots a DRB-selectable area of the
external user device 1104, and the external user device 1104 having
received the information selects the DRB for the discovery signal
in the DRB-selectable area corresponding to the information.
[0089] Certain embodiments of the present disclosure implement
various DRB selection methods by a combination of the DRB selection
method of the user device located in the dense area described in
FIGS. 10A to 10C and the resource partitioning method of the
external user device described in FIG. 11.
[0090] FIG. 12 illustrates examples of a DRB selection method
according to various embodiments of the present disclosure.
[0091] In certain embodiments, with regard to the DRB selection
method, one of three DRB allotment methods are selected according
to a condition requested by the user device located in the dense
area, and the external user devices are divided into two types
according to separation from the dense area discovery resources. In
certain embodiments, the DRB selection method is described by six
cases as shown in FIG. 12.
[0092] The DRB selection method of the user device located in the
dense area are separated by the following criteria. First, if the
minimum condition of additional overhead is required and the
additional operation of the user device is not required, without
considering the peripheral device, in selecting the DRB of the user
device located in the dense area, if the user device located in the
dense area selects the DRB from among the DRBs constituting the
dense area discovery resources. Second, if the overhead and delay
due to the additional operation of the user device is allowed or
the interference with the user device located in the dense area
exceeds a predetermined threshold in selecting the DRB of the user
device located in the dense area, if the user device located in the
dense area collects power of the subframes constituting the dense
area discovery resources. One of the DRBs constituting the subframe
with the lowest power is selected. Third, if adopting the
peripheral device for managing the dense area, the peripheral
device manages information on the DRBs allotted to the user devices
located in the dense area. If a new user device enters the dense
area, the peripheral device selects the DRB for the new user device
from the DRBs constituting the available resources in the dense
area discovery resources by a subframe unit and a subcarrier unit
so that the selected DRB has a uniform interval from the
pre-allotted DRBs.
[0093] If the external user device located outside the dense area,
the DRB is selected according to the resource partitioning method
by which the DRB is selected from the remaining area except for the
dense area discovery resources or the method by which the DRB of
the external user device is selected regardless of the dense area
discovery resources.
[0094] Based on the criteria above, referring to FIG. 12, the
method #1 (1200) refers to a method by which the DRB of the user
device located in the dense area is selected according to the first
criterion and the DRB of the external user device is selected
without applying the resource partitioning method. The method #2
(1204) refers to a method by which the DRB of the user device in
the external area is selected in the same manner as that of the
method #1 and the DRB of the user device in the dense area is
selected according to the second criterion above. The method #3
(1206) refers to a method by which the DRB of the user device in
the dense area is selected according to the third criterion and the
DRB of the external user device is selected without applying the
resource partitioning method.
[0095] The method #4 (1208) refers to a method by which the DRB of
the user device in the dense area is selected according to the
first criterion and the DRB of the external user device is selected
by applying the resource partitioning method. The method #5 (1210)
refers to a method by which the DRB of the user device in the dense
area is selected according to the second criterion and the DRB of
the external user device is selected by applying the resource
partitioning method. The method #6 (1212) refers to a method by
which the DRB of the user device in the dense area is selected
according to the third criterion and the DRB of the external user
device is selected by applying the resource partitioning
method.
[0096] FIG. 13 illustrates the operation of a user device according
to certain embodiments of the present disclosure.
[0097] In step 1300, the user device for D2D communication
determines whether its own current position belongs to the dense
area. This step is performed according to the criterion for dense
area determination described above. The criterion for dense area
determination has already been described before, so the detailed
description thereof will be omitted here. In step 1305, if the
current position of the user device does not belong to the dense
area as the result of the determination in step 1300, the user
device performs a typical operation for D2D communication.
[0098] In step 1310, if the current position of the user device
belongs to the dense area as the result of the determination, the
user device selects the DRB for the discovery signal, based on the
resources dedicated for the dense area. The resources dedicated for
the dense area is selected using any one of six methods shown in
FIG. 12. In step 1315, the user device transmits the discovery
signal using the selected DRB.
[0099] FIG. 14 illustrates a user device according to various
embodiments of the present disclosure.
[0100] Referring to FIG. 14, the user device 1400 includes a
controller 1405, a transmitting/receiving unit 1410, a dense area
determining unit 1415, and a resource allotting unit 1420. The
sub-units of the user device 1400 are only examples for convenience
of explanation and can be combined as one unit or divided into
sub-units for detailed operations according to certain embodiments
or the desire of service providers.
[0101] The dense area determining unit 1415 determines whether the
current position of the user device 1400 belongs to the dense area,
according to the criterion for dense area determination set forth
above. If the user device 1400 is determined to be located in the
dense area, the resource allotting unit 1420 selects the DRB for
the discovery signal in one of six DRB selection methods shown in
FIG. 12 based on the resources dedicated for the dense area. The
transmitting/receiving unit 1410 transmits the discovery signal
using the selected DRB.
[0102] FIG. 15 illustrates an example of a network environment to
which resource partition is applied according to various
embodiments of the present disclosure.
[0103] In certain embodiments, the network environment follows
2-Tier Network Option 1 that has been decided in the 3rd Generation
Partnership Project Radio Access Network (3GPP RAN)-1 conference.
Referring to FIG. 15, in the cell configuration 1500, an inter-site
distance between base stations installed in each cell is 500 meters
and each cell includes three sectors. A building, which is 120
meters long and 50 meters wide, is randomly located in each cell.
For example, 150 user devices are disposed in each sector, wherein
100 user devices are located in the dense area. In addition, 20
user devices and 30 user devices are located inside and outside the
cars and small buildings (hereinafter, referred to as "virtual
indoor places"), respectively. For example, the dense area
discovery resources 1505 (time-frequency) for the discovery signal
are comprised of N.sub.F.times.N.sub.T=44.times.50=2,200 DRBs.
N.sub.F denotes the number of partial blocks of frequency
resources, and N.sub.T denotes the number of partial blocks of time
resources. Based on the network environment and the dense area
discovery resources, the user device, according to certain
embodiments of the present disclosure, selects the DRB for
transmitting the discovery signal in any one of six methods
described in FIG. 12 according to its own position with respect to
the dense area. In certain embodiments, in evaluating performance
about repetition of a discovery section for D2D communication, DRB
hopping is randomly made with respect to each rule.
[0104] FIG. 16 illustrates the performance result if resource
partition is applied to a single discovery section according to
certain embodiments of the present disclosure. In certain
embodiments, the performance result is based on the network
environment of FIG. 15.
[0105] Referring to FIG. 16, the X-axis shows the number of user
devices discovered by the main user device, and the Y-axis shows
the probability of discovering the number of user devices
discovered as a cumulative distribution function (CDF). The
performance result graph shows the results of a virtual indoor
place, a dense area, and an outdoor place, respectively. In certain
embodiments, if the resource partition is applied, the performance
of the user devices in the dense area is considerably enhanced. If
the resource not selected by the user device of the dense area is
used in the outdoor place, the discovery performance improves due
to a decrease in interference. The average number of discovered
user devices by the main user device is lowest in the methods,
shown in FIG. 12, not applying the resource partition. Of the
methods shown in FIG. 12 where the resource partition is applied,
the average number of discovered user devices is highest in method
#6.
[0106] FIG. 17 illustrates the performance result by each area
where resource partition is applied according to various
embodiments of the present disclosure.
[0107] Referring to FIG. 17, if the resource partition is
performed, the performance of the user device located in the dense
area is noticeably improved compared to the performance of the user
device located in the outdoor place or in the virtual indoor
place.
[0108] FIG. 18 illustrates the performance result if resource
partition is applied to a repetition discovery section according to
certain embodiments of the present disclosure.
[0109] FIG. 18 shows the result of measuring the number of
discovered user devices, which are accumulated in each discovery
section. In certain embodiments, the average number of discovered
user devices in the methods #1 to #6 is more than that of the
random method that does not adopt the resource partition. The
performance sharply increases at initial repetition of the
discovery section (the first period), and, after repetition, the
average number of discovered user devices remains constant after
the 64th period in each method. The method #6 exhibits the highest
performance in a single discovery section, whereas there is little
or no difference between the methods #1 to #6 according to the
embodiment of the present disclosure in the repetition discovery
sections. In the repetition discovery sections, even without using
complicated methods, such as a perfect resource partition,
selection of the DRB having a uniform interval by a subframe unit
and a subcarrier unit, or the like, the performance is enhanced
only by randomly selecting the DRB in the dense area discovery
resources.
[0110] Although the present disclosure has been described with an
exemplary embodiment, various changes and modifications may be
suggested to one skilled in the art. It is intended that the
present disclosure encompass such changes and modifications as fall
within the scope of the appended claims.
* * * * *